Filter device

ABSTRACT

A filter device having a plurality of filter elements ( 23 ) that can be received in a filter housing ( 1 ) having a filter inlet ( 19 ) for a fluid that is to be filtered and a filter outlet ( 21 ) for the filtered fluid, wherein flow can pass through the filter elements ( 23 ) for a filtration or backwash in both directions and wherein at the same time at least one filter element ( 23 ) performs the filtration and at least one other filter element ( 23 ), for cleaning off the active filter surface thereof, can be backwashed by means of a backwash appliance which, for supporting the backwashing, contains a pressure control appliance ( 43 ) which has a pressure control element ( 45 ) by means of which, during a backwash operation, the fluid flow is controllable in a fluid connection between filter inlet ( 19 ) and the filter element ( 23 ) that is to be cleaned off, is characterized in that the fluid connection has a connection space ( 29 ) having element openings ( 27 ) each of which can be connected to an open end of the filter cavity forming the unfiltered side of each filter element ( 23 ), in that a fluid pathway ( 27 ) is provided via which, during the filtration, unfiltrate flows into the connection space ( 29 ) and in that, by means of the pressure control element ( 45 ), the flow of unfiltrate through the element opening ( 27 ) associated with the filter element ( 23 ) that is to be cleaned off can be controlled.

The invention relates to a filter device having a plurality of filter elements, which can be received in a filter housing having a filter inlet for a fluid that is to be filtered, and a filter outlet for the filtered fluid, wherein flow can pass through the filter elements in both directions for filtration or backwash, and wherein at the same time, at least one filter element performs the filtration, and at least one other filter element for cleaning off the active filter surface thereof can be backwashed by means of a backwash mechanism, which includes a pressure control mechanism for supporting the backwash, which has a pressure control element, by means of which the fluid flow in a fluid connection between filter inlet and the filter element that is to be cleaned off can be controlled during a backwash operation.

A filter device of this type is disclosed in EP 2 207 609 B1. In the known apparatus, conically shaped filter elements are provided, in particular in the form of so-called slotted screen pipe elements. Due to the conical design, the spacing between the individual slotted screen pipe elements is increased in regions, as a result of which the volute in the filter housing is also enlarged. In the case of backwashing, the conical filter element has a clear advantage over a cylindrical filter element. One reason for this is the relatively larger outlet cross-section of the filter elements at the lower end as compared to cylindrical filter elements having the same filter surface, because the larger outlet cross-section at the lower end facilitates the discharge of contamination with the backwash fluid. The pressure control element of the pressure control mechanism, which controls a flow of unfiltrate to the backwashing filter element in order to support the backwash, is allocated to the upper, open end of the relevant filter element, which due to the conical shape thereof, has a smaller opening cross-section.

Accordingly, in the known apparatus, the filter inlet for the supply of the unfiltrate is located above the filter elements, so that during filtration, the unfiltrate flows into the filter cavities by means of the openings that have the smaller opening cross-section, which is not optimal in terms of flow resistance.

In view of the prior art, the object of the invention is to provide a filter device, which is characterized by improved flow characteristics during operation.

This object is achieved according to the invention by a filter device having the characteristics of claim 1 in its entirety.

Pursuant to the characterizing portion of claim 1, an essential feature of the invention is that the fluid connection between the filter inlet of the filter housing and the respective filter element that is to be cleaned off has a connecting chamber having element openings, each of which can be connected to an open end of the filter cavity, forming the unfiltered side of each filter element in that a fluid pathway is provided, by means of which unfiltrate flows into the connecting chamber during filtration, and that the flow of unfiltrate through the element opening associated with the filter element that is to be cleaned off can be controlled by means of the pressure control element in such a way that, as is also the case in the known apparatus, a suction effect that aids the backwash is generated on the unfiltered side of the filter element that is to be cleaned off. Since, to this end, the unfiltrate does not pass to the upper end of the filter cavities having the relatively smaller opening cross-section, due to a direct connection of the filter inlet of the filter housing, but rather from the connecting chamber, the element openings thereof being connected to the unfiltered sides of the filter elements, this eliminates the need to dispose the filter inlet of the housing in such a way that the flow of unfiltrate passes through the opening of the smaller cross-section into the filter cavities during filtering. Thus it becomes possible to dispose the filter inlet in such a way that the lower openings having the larger cross-section form the fluid inlets for the filtration, whereby improved flow conditions with reduced flow resistance are achieved.

It is particularly advantageous for the improved rinsing performance within the context of the respective backwashing operation, that a tangential flow (cross flow) be applied from top to bottom in the element that is to be backwashed with a very high flow rate, which leads to significant cleaning results in the manner of a bypass connection. Through the pressure control mechanism, closing an element opening leads to a kind of pressure surge in the system and any particulate contamination remaining in the element will be removed in a pulsed manner from the element by means of the pressure surge. Overall, there is a kind of free jet effect on the filter surface that is to be cleaned off, thus viewed in a tangential direction, a kind of shear layer with suction.

The apparatus according to the invention is especially suitable for ballast water systems of ships in order to avoid the unwanted entry of foreign microorganisms, plants, etc. in waters in which these species are not indiginous. In conventional automatic filters, the differential pressure Δp between the filtrate side and the backwash line of the apparatus determines the cleaning result, which to that extent is limited thereby, which is not the case with the solution according to the invention having a pressure control mechanism, since in this case, higher differential pressures in Δp can be reliably controlled. Due to the connecting chamber, a large quantity of fluid for tangential flushing is available in the first rinsing phase, which likewise improves the cleaning performance of the apparatus.

It has been shown that, compared to conventional systems having backwashing with additionally high levels of contaminate ingress, it is no longer possible for the elements to become blocked, which then requires regular manual washing, but rather, when using the pressure control mechanism, pulsed cleaning is always sufficient to control increased contamination and to always successfully clean the element. The solution according to the invention is also able to handle very long backwashing, as is common in ships, and ideally, the filter elements are cleaned with very low filtrate pressures. The respective apparatus can be constructed out of individual, standardized components, which in this respect leads to a modular system that can be easily adapted to the respective application.

Since the filter cavity of the filter elements forms the unfiltered side during filtration, the open ends of the filter cavities forming the unfiltered side and the element openings of the connecting chamber can form parts of the fluid pathway for the inflow of unfiltrate into the connecting chamber.

In modified embodiments, the arrangement may be such that the fluid pathway has a bypass line, which connects the filter inlet with the connecting chamber. In addition, a pump can be provided, which boosts the inflow of unfiltrate in the bypass line, which can be controlled if needed in such a way that when initiating backwashing, a flow of unfiltrate of appropriate intensity is provided.

In advantageous embodiments, each element opening of the connecting chamber is assigned to a separate pressure control element.

Alternatively, a pressure control element that is jointly assigned to the element openings can be provided, which can be moved by means of a displacement mechanism in operative connection with the element opening of the respective filter element that is to be backwashed.

In especially advantageous embodiments, the respective pressure control element is a pneumatically actuated cut-off valve. It is advantageous that, for the operation of the filter device, a compressed air supply can be used such as is frequently installed in the facilities or buildings in which filter devices of this kind are frequently used.

In especially advantageous embodiments, the filter elements, in the manner of filter cartridges, in particular in the form of slotted screen pipe elements, are disposed vertically in the filter housing, and with the upper, open end of the filter cavity thereof forming the unfiltered side being connected to the element openings of the connecting chamber during the filtering, wherein the filter elements adjoin an inflow space at the open, lower ends of their filtering hollow chamber, into which the filter input of the filter housing opens for the supply of unfiltrate. During the filtering process, the lower opening of the filter elements, having the larger cross-section thereby, forms the inlet opening for the unfiltrate that flows from the inflow space of the filter housing, while the lower opening of the respective filter element that is to be backwashed forms the outlet opening for discharging the contaminate-laden backwash fluid. In an alternative⁻embodiment, at least one bypass line can also connect the inflow space with the connecting chamber in a fluid-conducting manner, preferably in a parallel construction to the filter cartridges.

For a backwash operation, the open, lower end of the filter cavity of the respective filter element that is to be cleaned off can be connected to a backwash line, by means of which fluid contaminated during backwashing is discharged, wherein the backwash line can be optionally blocked and released by means of a valve mechanism.

The invention is explained in detail below with reference to embodiments shown in the drawings. Shown are:

FIG. 1 schematic representation, not to scale, of a longitudinal section of an embodiment of the invention;

FIG. 2 an enlarged partial view as compared to FIG. 1 of the region designated as II in FIG. 1;

FIG. 3 a view similar to that in FIG. 1, wherein the flow pattern before carrying out the backwash of a selected filter element is indicated;

FIG. 4 a view similar to that in FIG. 3, wherein the flow pattern during the backwash of a selected filter element is indicated;

FIG. 5 an enlarged view as compared to FIG. 4 of only the region designated as V in FIG. 4;

FIG. 6 a partial, broken off cross-sectional view of the upper part of the apparatus of a modified embodiment in approximately the same scale as FIG. 5, and

FIG. 7 a longitudinal sectional view, in a scale that is smaller than in the preceding Figure, of a further modified embodiment.

The filter device shown in FIGS. 1 to 5 has a cylindrical filter housing 1 having a body 3, an upper cover part 5 and a lower housing closure 7. An intermediate bottom 9 is located between this housing closure and the body 3. A cover plate 11 extends between the housing body 3 and the cover part 5. As the Figures show, these parts are flanged with one another by means of flange connections 13. The intermediate bottom 9 separates the inner space 15 located in the body 3, which forms the clean side of the filtrate space, from the inflow space 17 inside the housing closure 7, into which the unfiltrate can flow by means of a filter inlet 19. The filter outlet 21 provided for the delivery of filtrate from the filtrate space 15 is located in the central area of the housing body 3.

The intermediate bottom 9 forms the element receptacle for filter elements 23 in the manner of filter cartridges, wherein in the present example, these are conical slotted screen pipe elements. The lower ends thereof, having a greater diameter, are accommodated on the intermediate bottom 9 that serves as an element receptacle in such a way that the inner filter cavities of the filter elements 23 are connected to the inflow space 17 in the housing closure 7, thus with the unfiltrate space, by means of through passages 25 in the intermediate bottom 9. The filter elements 23 are disposed at spacings from one another along an arc that is concentric to the central axis of the filter housing 1. In an embodiment according to the illustration in FIG. 6, filter elements can also be disposed in groups along a plurality of arcs.

The upper, open ends of the filter elements 23, which are opposite the intermediate bottom 9, are connected to element openings 27, which are formed in the cover plate 11, and which form openings of a connecting chamber 29 located between the cover plate 11 and cover part 5. As can be seen most clearly in FIG. 2, this forms an overflow duct, which connects the filter cavities of the filter elements 23 with one another by means of the element openings 27. Since, during the filtration, the filter cavities are connected to the filter inlet 19 for unfiltrate by means of the inflow space 17, the connecting chamber 29 forms an unfiltrate space.

The flow pattern when the filtration is in operation is indicated in FIGS. 1 and 2 with flow arrows 31, which are not all numbered, wherein infiltrate flows into the inner filter cavities of the filter elements 23 by means of the through passages 25 on the intermediate bottom 9, flows through the filter elements 23 from inside to the outside to the filtrate space 15, from where the filtrate exits by means of the filter outlet 21. In order to perform the backwash on a filter element 23 that is to be cleaned off, a movable backwash arm 33, which is connected to a backwash line 35 that leads outward, is connected to the through passage 25 of the filter element 23 selected for cleaning. The backwash line 35 can be selectively shut and released by means of a valve mechanism 37. In order to move the backwash arm 33 into an appropriate backwash position, a drive device is provided, by means of which the backwash arm 33 can be pivoted in an arc according to the arrangement of the filter element 23. The drive mechanism has a drive motor 39 disposed on the cover part 5, which drives the backwash arm 33 by means of a drive shaft device 41, which is disposed coaxially in the filter housing 1.

In order to facilitate the backwash operation, the backwash mechanism has a pressure control mechanism, which generates a suction effect within the filter cavity forming the unfiltered side of the filter element 23 that is to be cleaned off by means of a pressure control element. This is done in such a way that the backwash arm 33 is aligned with the filter element 23 that is to be cleaned, wherein in the illustration in the Figures, it is the left side of each filter element 23 that is visible. After the backwash line 35 is released by opening the valve 37, a flow of unfiltrate develops in the selected filter element 23 as a result of the overflow effect of the connecting chamber 29, which flows from the upper element opening 27, through the through passage 25 in the intermediate bottom 9, to the backwash arm 33. By means of the movable pressure control element of the pressure control mechanism, the flow rate is now slowed by controlling the aperture at the corresponding element opening 27 in such a way that a hydrodynamic suction effect is generated in the filter cavity.

FIGS. 3 to 5 show the corresponding sequence of functions. In the present example, the pressure control mechanism has a pneumatically actuated cut-off valve 43 as a pressure control element, which has a movable valve body 45, by means of which the aperture of the respective element opening 27 of the corresponding filter element 23 can be controlled. In the present example, the valve body 45, in combination with the edge of the element opening 27 on the cover plate 11, forms a kind of disc valve, so that closing the cut-off valve 43 effects an abrupt interruption in flow and a suction effect in the manner of a pressure surge is thereby generated. Instead of an abrupt and/or complete shutting of the valve, a desired slowing of the flow rate can be achieved by not completely stopping, but rather by throttling the flow.

As already mentioned, FIGS. 1 and 2 show filtration during operation, wherein, as can be seen most clearly in FIG. 2, the element openings 27 on all of the filter elements 23 are open. Accordingly, the valve bodies 45 of the cut-off valves 43, each element opening 27 of which is allocated to its own cut-off valve 43, are in the raised position, as shown in FIGS. 1 and 2. In order to initiate a backwash operation, the cut-off valve 43 on the element opening 27 of the selected filter element 23 is closed, the backwash arm 33 is aligned with the through passage 25 of the selected filter element 23 on the intermediate bottom 9, and the backwash line 35 is released by means of the valve mechanism 37. Briefly opening the cut-off valve 43 on the selected filter element 23 creates a flow of unfiltrate from the connecting chamber 29 through the filter cavity to the backwash line 35. This operational state is shown in FIG. 3. FIGS. 4 and 5 show the status of the interruption of flow according to the previous, brief opening of the cut-off valve 43, which results in a suction effect for filtrate flowing in from the housing space 15, as the flow arrows 47 with solid lines show. Thus, not only is the pressure prevailing on the clean side available for the backwash, but an increased pressure gradient is also available for cleaning at the filter element 23, so that even stubborn contamination can be cleaned and discharged by means of the backwash line 35 when the valve mechanism 37 is opened.

In the example in FIGS. 1 to 5, the element openings 27 for each filter element 23 are assigned to a separate cut-off valve 43 as a pressure control mechanism. The pneumatically activated cut-off valves 43 each have a pneumatic cylinder 51, having a piston 53 that can be moved by means of a piston rod 55, for the associated valve body 45.

In the embodiment in FIG. 6, filter elements 23 are disposed along two concentric arcs, so that two circles of holes are located in the cover plate 11, which form the element openings 27 of the connecting chamber 29. FIG. 6 only shows, however, two of the filter elements 23 assigned to the outer circle of holes. An additional difference as compared to the example described above is that each circle of holes is assigned to only one cut-off valve 43. Each of these pneumatically actuated valves 43 is located on a valve arm 57, which is rotated by the drive motor 39, together with the backwash arm 33, wherein the control and actuation is done by means of pneumatic lines 59, and a backwash arm 33 is provided for each row of filter elements 23, which are not visible in FIG. 6. Aside from this, the functioning corresponds to that of the example described above.

FIG. 7 shows a further embodiment, which only differs from the example in FIG. 6 in that the fluid pathway, by means of which unfiltrate flows into the connecting chamber 29 during filtration, is not created exclusively by means of element openings 27 in the connecting chamber 29, thus out of the inner filter cavity of the filter elements 23, but that in addition, a connection between the filter inlet 19 and the connecting chamber 29 is provided as a fluid pathway, forming a bypass. In the illustration in FIG. 7, an external bypass line 63 is provided for this purpose, which extends along the outside of the housing and in which a pump 65 is also disposed to support the flow.

Instead of an external bypass line 63, at least one branch line could be provided within the housing body 3 between the lower inflow space 17 and the connecting chamber 29, which is not shown in the Figure.

While in the examples in FIGS. 6 and 7, each hole of circles having element openings 27 is assigned to a single cut-off valve 43 on a valve arm 57, a stationary cut-off valve 43 could be provided at each element opening 27, wherein the pivotable valve arms 57 could move these stationary cut-off valves 43 mechanically against a closing force into an open position in the event of an overflow. Further, it is understood that instead of the pneumatic actuation that is shown, other kinds of valve actuators could be provided, for example hydraulic or electric valve actuators. 

1. A filter device having a plurality of filter elements (23), which can be received in a filter housing (1) having a filter inlet (19) for a fluid that is to be filtered, and a filter outlet (21) for the filtered fluid, wherein flow can pass through the filter elements (23) in both directions for filtration or backwash, and wherein at the same time, at least one filter element (23) performs the filtration, and at least one other filter element (23) for cleaning off the active filter surface thereof can be backwashed by means of a backwash mechanism, which includes a pressure control mechanism (43) for supporting the backwash, which has a pressure control element (45), by means of which the fluid flow in a fluid connection, between filter inlet (19) and the filter element (23) that is to be cleaned off, can be controlled during a backwash operation, characterized in that the fluid connection has a connecting chamber (29) having element openings (27), each of which can be connected to an open end of the filter cavity forming the unfiltered side of each filter element (23), in that a fluid pathway (27; 63) is provided, by means of which unfiltrate flows into the connecting chamber (29) during filtration, and in that, by means of the pressure control element (45), the flow of unfiltrate though the element opening (27), associated with the filter element (23) that is to be cleaned off, can be controlled.
 2. The filter device according to claim 1, characterized in that element openings (27) of the filter cavities forming the unfiltered side form parts of the fluid pathway for the inflow of unfiltrate into the connecting chamber (29).
 3. The filter device according to claim 1, characterized in that the fluid pathway has a bypass line (63), which connects the filter inlet (19) with the connecting chamber (29).
 4. The filter device according to claim 1, characterized in that a pump (65) is provided, which boosts the inflow of unfiltrate in the bypass line (63).
 5. The filter device according to claim 1, characterized in that each element opening (27) is allocated to its own pressure control element (45).
 6. The filter device according to claim 1, characterized in that a pressure control element (45) jointly assigned to multiple element openings (27) is provided, which can be moved by means of a displacement mechanism (41, 57) in an operative connection with the element opening (27) of the respective filter element (23) that is to be backwashed.
 7. The filter device according to claim 1, characterized in that each element opening (27) is alloicated to is own pressure control element (45).
 8. The filter device according to claim 1, characterized in that a pressure control element (45), jointly assigned to the element openings (27), is provided, which can be moved by means of a displacement mechanism (41, 57) in operative connection with the element opening (27) of the respective filter element (23) that is to be backwashed.
 9. The filter device according to claim 1, characterized in that the respective pressure control element is a pneumatically actuated cut-off valve (43).
 10. The filter device according to claim 1, characterized in that a cut-off valve (43) is provided, which allows an abrupt blocking process.
 11. The filter device according to claim 1, characterized in that the filter elements (23), in the manner of filter cartridges, are disposed vertically in the filter housing (1), and the upper, open end of the filter cavity thereof, forming the unfiltered side, being connected to the element openings (27) of the connecting chamber (29) during the filtration, and in that the open, lower end of the filter elements (23) adjoin an inflow space (17), into which the filter input (19) of the filter housing (1) opens, for the supply of unfiltrate.
 12. The filter device according to claim 1, characterized in that, for a backwash operation, the lower open end of the filter cavity of the respective filter element (23) that is to be cleaned off can be connected to a backwash line (35), by means of which fluid contaminated during backwashing is discharged.
 13. The filter device according to claim 1, characterized in that the backwash line (35) can be optionally blocked and released by means of a valve mechanism (37).
 14. The filter device according to claim 1, characterized in that the backwash mechanism has a movable backwash arm (33), which can be connected to the lower, open end of the filter element (23) that is to be cleaned off by means of a drive mechanism (39, 41). 